Semiconductor memory device allowing acceleration testing, and a semi-finished product for an integrated semiconductor device that allows acceleration testing

ABSTRACT

A DRAM includes a row predecoder responsive to an multi-selection signal for activating all predecode signals independent of a row address signal, and a row decoder unit responsive to the multi-selection signal for activating all decode signals independent of the row address signal. As a result, all word drivers are activated in an acceleration test independent of the row address signal, and all the word lines are driven simultaneously.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor memory device and asemi-finished product for an integrated semiconductor device. Moreparticularly, the present invention relates to a semiconductor memorydevice that allows an acceleration test such as a burn-in test, and asemi-finished product for an integrated semiconductor device that allowssuch testing in a wafer state prior to dicing.

2. Description of the Background Art

FIG. 39 is a block diagram schematically showing a structure of a memorycell and a row decoder widely used in a dynamic random access memorydevice (referred to as DRAM hereinafter). Referring to FIG. 39, a memorycell 111 includes an access transistor 112 and a cell capacitor 113,connected to a corresponding word line WL and a bit line BL. A rowdecoder selecting one word line in response to a row address signalincludes a row predecoder 121a, a predecode signal line 122, and aplurality of word drivers. One word driver is provided corresponding toeach word line WL. In FIG. 39, only one word driver WD is typicallyshown. Row predecoder 121a predecodes row address signals RA1-RA4 andcomplementary row address signals /RA1-/RA4 to generate predecodesignals X1-X8 which are supplied to predecode signal line 122. Each worddriver is activated in response to one of predecode signals X1-X4 andone of predecode signals X5-X8. When the word driver is rendered active,a boosted potential VPP higher than the power potential VPP higher thanthe power supply potential is supplied to a corresponding word line.

Word driver WD includes N channel MOS transistors 124 and 125 connectedin series between a precharge node NX and a ground node, P channel MOStransistors 126 and 127 connected in parallel between a boosting node towhich boosted potential VPP is supplied and precharge node NX, and a Pchannel MOS transistor 128 and an N channel MOS transistor 129 forming aCMOS inverter. During an inactive period of the DRAM (chip), a prechargesignal PR of an L level (logical low) is applied to the gate electrodeof transistor 126. In response, precharge node NX is precharged to an Hlevel (logical high). Therefore, all the word lines are fixed to an Llevel when the chip is inactive. When the chip is activated, prechargesignal PR is pulled up to an H level from an L level, whereby theprecharge operation of node NX by transistor 126 is suppressed. However,word line WL maintains its L level since node NX is held at the H level.This is because the potential of word line WL is fed back to the gateelectrode of transistor 127, whereby transistor 127 continuouslysupplies charge to node NX. Therefore, the charge of node NX must bedischarged towards the ground node in order to render word line WLactive. This word driver WD has both transistors 124 and 125 turned onwhen one predecode signal DECA out of predecode signals X1-X4 attains anH level and one predecode signal DECB out of predecode signals X5-X8attains an H level. As a result, the potential of node NX is pulled downtowards the L level, whereby transistors 128 and 129 are turned on andoff, respectively. Thus, word line WL is activated, so that thepotential thereof is boosted to the level of the boosted potential VPP.

FIG. 40 is a circuit diagram showing a structure of row predecoder 121ashown in FIG. 39. Referring to FIG. 40, row predecoder 121a includes NORgates 1211-1218, inverters 1221a-1228a and 1231-1238. Each of NOR gates1211-1214 receives either row address signal RA1 or a complementary rowaddress signal /RA1, and either row address signal RA2 or acomplementary row address signal /RA2. Each of NOR gates 1215-1218receives either a row address signal RA3 or a complementary row addresssignal RA3, and either a row address signal RA4 or a complementary rowaddress signal /RA4. Each of NOR gates 1211-1218 has its output signalprovided to a word driver as a predecode signal via two inverters. Forexample, NOR gate 1211 receives row address signals /RA1 and /RA2 toprovide predecode signal X1 to the word driver via two inverters1221a-1231. Therefore, one of predecode signals X1-X4 attains an H levelaccording to four combinations of row address signals RA1, /RA1, RA2,and /RA2. For example, predecode signal X1 attains an L level when rowaddress signals /RA1 and /RA2 both attain an L level. Furthermore,according to the four combinations of row address signals RA3, /RA3, RA4and /RA4, one of predecode signals X5-X8 attains an H level. Forexample, when row address signals /RA3 and /RA4 both attain an L level,predecode signal X5 is pulled up to an H level.

In order to carry out a stress test on word line WL and accesstransistor 112 in the above-described DRAM, boosted potential VPP mustbe supplied to word line WL only during a predetermined time period.However, the testing is time-consuming according to increase in thecapacity of a memory, resulting in increase in the cost required fortesting. For example, a reliability test called "burn-in" that appliesacceleration stress on a memory cell had a problem that the testing timeperiod becomes longer as the number of memory cells becomes greater. Thestress testing on a gate oxide film in access transistor 112 and on adielectric film in cell capacitor 113 are extremely important. However,the number of word lines n that can be activated at one time is limitedin a normal operation. Therefore, the testing must be carried for N(total number of word lines) /n times in order to evaluate all the wordlines. The time required for testing becomes longer in accordance with ahigher integration density of a chip.

A method of increasing the number of word lines that are activatedsimultaneously is considered as one way of reducing the testing time. Anexample of an DRAM that allows testing by such a method is shown in FIG.41. FIG. 41 is substantially identical to FIG. 3 in pp. 639-642 of"IEDM93, DIGEST". Referring to FIG. 41, the DRAM includes a memory cellarray 11 having a plurality of word lines WL and bit lines (not shown)crossing thereto, a row decoder 12 selecting one of word lines WL, acolumn decoder 13 selecting one bit line, and a plurality of N channelMOS transistors 1 connected corresponding to word lines WL. Row decoder12 includes a plurality of word drivers WD, each driving a correspondingword line WL. All transistors 1 are turned on in response to onemulti-selection signal MLT, whereby boosted test potential VST issupplied to all word lines WL. Therefore, stress can be applied to allthe access transistors simultaneously since all the word lines areactivated in a burn-in mode. Thus, the testing time can be shortened.

FIG. 42 shows a semiconductor (silicon) wafer 70 not yet subjected to adicing process. A plurality of semiconductor chips 71 are formed onsilicon wafer 70. A probe card 2 as shown in FIG. 43 is used in carryingout an acceleration test such as burn-in on the wafer shown in FIG. 42.Probe card 2 includes an opening 3 corresponding to a plurality of chips71 aligned in one row in the vertical direction (three in FIG. 42) inwafer 70. A plurality of probes 4 are provided corresponding to thethree chips 71 at the periphery of opening 3. This probe card 2 is seton wafer 70 to carry out a burn-in test in a wafer state. Probes 4 arebrought into contact with the pads (not shown) of the three chips 71, sothat power supply and a signal for testing can be applied simultaneouslyto the three chips 71. In order to test all the chips 71 in wafer 70,the setting position of probe card 2 must be shifted 5 times.

Since boosted test potential VST is supplied to word line WL viatransistor 1 in the DRAM of FIG. 41, boosted test potential VST must behigher than boosted potential VPP by the threshold voltage of transistor1 in order to supply a boosted potential VPP higher than the powersupply potential to word line WL. Therefore, a great stress is appliedon transistor 1 controlled by multi-selection signal MLT which isgreater than that on the access transistor that should actually receivethe greater stress. As a result, there is a possibility that thesetransistors 1 become defective. Furthermore, since one transistor 1 mustbe provided corresponding to each word line WL, reduction in the pitchbetween word lines WL due to miniaturization of the chip is attributedto the difficulty of forming a transistor with such small pitches. As aresult, there is a possibility that these transistors 1 becomedefective.

When silicon wafer 70 as shown in FIG. 42 is to be tested using probecard 2 shown in FIG. 43, the setting position of probe card 2 must bechanged 5 times with respect to wafer 70. There was a problem that theentire testing of wafer 70 was time consuming.

SUMMARY OF THE INVENTION

In view of the foregoing, one object of the present invention is toprovide a semiconductor memory device of a simple structure that allowsacceleration testing by activating a plurality of word linessimultaneously.

Another object of the present invention is to provide a semi-finishedproduct for an integrated semiconductor device that allows accelerationtesting in a wafer state at a short time period.

According to an aspect of the present invention, a semiconductor memorydevice can be operated in a normal mode and a test mode. Thesemiconductor memory device includes a plurality of word lines, aplurality of bit lines, a plurality of memory cells, a plurality ofdrive circuits, and an activation circuit. The plurality of bit linescross the word lines. The plurality of memory cells are providedcorresponding to respective crossings of a word line and a bit line.Each memory cell is connected to a corresponding word line and bit line.The plurality of drive circuits are provided corresponding to the wordlines. Each drive circuit drives a corresponding word line. Theactivation circuit selectively activates one drive circuit in responseto an externally applied row address signal when in a normal mode, andactivates at least two drive circuits in response to a predeterminedmulti-selection signal and independent of a row address signal in a testmode.

The above semiconductor memory device has one drive circuit selectivelyactivated in response to an externally applied row address signal in anormal mode, whereby a corresponding word line is driven. In a testmode, at least two drive circuits are activated in response to apredetermined multi-selection signal and independent of a row addresssignal in a test mode, whereby at least two word lines are driven. Thus,the testing time is shortened.

According to another aspect of the present invention, a semiconductormemory device can be operated in a normal mode and a test mode. Thesemiconductor memory device includes a plurality of word line groups, aplurality of bit lines, a plurality of memory cells, a plurality ofdrive circuits, and an activation signal. Each word line group includesa plurality of word lines. The plurality of word lines cross a wordline. The plurality of memory cells are provided corresponding torespective crossings of a word line and a bit line. Each memory cell isconnected to a corresponding word line and a bit line. The plurality ofdrive circuits are provided corresponding to the word lines. Each drivecircuit drives a corresponding word line. The activation circuitselectively activates one drive circuit in response to an externallyapplied row address signal when in a normal mode, and activates all thedrive circuits corresponding to one word line group in response to aplurality of multi-selection signals supplied corresponding to a wordline group when in a test mode.

The above-described semiconductor memory device has one drive circuitselectively activated in response to an externally applied row addresssignal when in a normal mode, whereby a corresponding one word line isdriven. When in a test mode, all the word lines in one word line groupare driven in response to multi-selection signals in a test mode.Therefore, a testing in which word lines are driven in a divisionalmanner can be carried out.

According to a further aspect of the present invention, a semiconductormemory device includes a semiconductor substrate, a plurality of wordlines, plurality of bit lines, a plurality of memory cells, a pluralityof drive circuits, an activation circuit, a substrate potential supplycircuit, a cell plate potential generation circuit, and a cell platepotential supply circuit. The plurality of word lines are formed on asemiconductor substrate. The plurality of bit lines are formed on thesemiconductor substrate crossing the word lines. The plurality of memorycells are provided corresponding to respective crossings of a word lineand a bit line. Each memory cell includes a cell capacitor and an accesstransistor. The cell capacitor is formed on the semiconductor substrate,and includes a cell plate and a storage node to store data. The accesstransistor includes a gate electrode, and one and the other source/drainregions. The gate electrode is formed on the semiconductor substrate,and is connected to a corresponding word line. One source/drain regionis formed in the semiconductor substrate, and is connected to acorresponding bit line. The other source/drain region is formed in thesemiconductor substrate, and is connected to the storage node of a cellcapacitor. The plurality of drive circuits are provided corresponding tothe word lines. Each drive circuit drives a corresponding word line. Theactivation circuit selectively activates one drive circuit in responseto an externally applied row address signal when in a normal mode, andactivates at least two drive circuits in response to a predeterminedmulti-selection signal regardless of a row address signal when in a testmode. The substrate potential supply circuit responds to multi-selectionsignal to selectively supply a predetermined substrate potential and apredetermined first test potential to the semiconductor substrate. Thecell plate potential generation circuit generates a cell plate potentialfor a cell plate. The cell plate potential supply circuit selectivelysupplies a cell plate potential from the cell plate potential generationcircuit and a predetermined second test potential to the cell plate inresponse to the multi-selection signal.

According to still another aspect of a semiconductor memory device ofthe present invention, one word line is activated and a predeterminedsubstrate potential is supplied to a semiconductor substrate in responseto an externally applied row address signal when in a normal mode,whereby a cell plate potential from a cell plate potential generationcircuit is supplied to a cell plate. In a test mode, a first testpotential is supplied to the semiconductor substrate, and the secondtest potential is supplied to the cell plate. The first test potentialis supplied to a storage node via the other source/drain region of theaccess transistor. Therefore, a predetermined voltage can be applied tothe cell capacitor of a memory cell.

According to a still further aspect of the present invention, anonvolatile semiconductor memory device can be operated in a normal modeand a data erasure mode. The nonvolatile semiconductor memory deviceincludes a plurality of word lines, a plurality of source lines, aplurality of floating gate type memory cells, a plurality of drivecircuits, and an activation circuit. The plurality of source lines crossthe word lines. The plurality of floating gate type memory cells areprovided corresponding to respective crossings of a word line and asource line. Each floating gate type memory cell is connected to acorresponding word line and a source line. The plurality of drivecircuits are provided corresponding to the word lines. Each drivecircuit drives a corresponding word line. The activation circuitselectively activates one drive circuit in response to an externallyapplied row address signal when in a normal mode, and activates at leasttwo drive circuits in response to a predetermined multi-selection signaland independent of an address signal in a data erasure mode.

The above-described nonvolatile semiconductor memory device has onedrive circuit activated in response to an externally applied row addresssignal in a normal mode, whereby a corresponding one word line isdriven. In a test mode, at least two drive circuits are activated inresponse to a multi-selection signal, whereby at least two word linesare activated. Therefore, data written in floating gate type memorycells can partially be erased.

According to yet another aspect of the present invention, asemi-finished product for an integrated semiconductor device includes asemiconductor wafer, a plurality of semiconductor chips, and a firsttest interconnection. The plurality of semiconductor chips are formed onthe semiconductor wafer to attain a test mode in response to an externaltest signal provided from the outside world. The first testinterconnection is provided on the semiconductor wafer and formed in aregion other than the region where the plurality of semiconductor chipsare located. The first test interconnection is connected in common tothe plurality of semiconductor chips, and receives an external testsignal.

In the above-described semi-finished product for an integratedsemiconductor device, the first test interconnection is formed on adicing region of a semiconductor wafer in which a plurality ofsemiconductor chips are formed. An external test signal is applied toall the semiconductor chips via the first test interconnection. Sinceall the semiconductor chips attain a test mode, the testing time under awafer state can be reduced.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an entire structure of a DRAMaccording to a first embodiment of the present invention.

FIG. 2 is a block diagram specifically showing a memory cell array, asense amplifier train, and an input/output circuit of FIG. 1.

FIG. 3 is a circuit diagram showing a specific structure of memory cellarray of FIG. 1.

FIG. 4 is a sectional view of one memory cell shown in FIGS. 2 and 3.

FIG. 5 is a circuit diagram showing a specific structure of amulti-selection pad and a multi-selection signal generation circuit ofFIG. 1.

FIG. 6 is a block diagram showing a specific structure of a row decoder12 of FIG. 1.

FIG. 7 is a block diagram showing a structure of the row predecoder andone word driver of FIG. 6.

FIG. 8 is a circuit diagram showing a specific structure of the rowpredecoder of FIGS. 6 and 7.

FIG. 9 is a circuit diagram showing a specific structure of a pluralityof row decoder units in FIG. 6.

FIG. 10 is a timing chart showing an operation of the DRAM shown inFIGS. 1-9.

FIG. 11 is a circuit diagram showing a specific structure of a rowpredecoder in an DRAM according to a second embodiment of the presentinvention.

FIG. 12 is a block diagram showing a circuit for generating twomulti-selection signals of FIG. 11.

FIG. 13 is a diagram for describing the manner of word lines driven in adivisional manner for every group according to the second embodimentshown in FIGS. 11 and 12.

FIG. 14 is a block diagram showing a structure of the main components ofan DRAM according to a third embodiment of the present invention.

FIGS. 15 and 16 are timing charts showing examples of operations of theDRAM shown in FIG. 14.

FIG. 17 is a block diagram showing a structure of the main components ofa DRAM according to a fourth embodiment of the present invention.

FIG. 18 is a timing chart showing an operation of the DRAM of FIG. 17.

FIG. 19 is a block diagram showing a structure of the main components ofa DRAM according to a fifth embodiment of the present invention.

FIG. 20 is a timing chart showing an operation of the DRAM of FIG. 19.

FIG. 21 is a block diagram showing a structure of the main components ofa DRAM according to a sixth embodiment of the present invention.

FIG. 22 is a circuit diagram showing a specific structure of a switchingcircuit and a selector at the bit line side of FIG. 21.

FIG. 23 is a circuit diagram showing a structure of switching circuitand a selector at the cell plate side of FIG. 21.

FIG. 24 is a block diagram showing a structure of the main components ofa DRAM according to a seventh embodiment of the present invention.

FIG. 25 is a timing chart showing an operation of the DRAM shown in FIG.24.

FIG. 26 is a diagram for describing the manner of testing semiconductorchips in a wafer state which do not have the boosted power supply padsof FIG. 24.

FIG. 27 is a plan view of a probe card used for testing thesemiconductor chip in FIG. 26 in a wafer state.

FIG. 28 is a diagram for describing a structure of the main componentsof a DRAM according to an eighth embodiment of the present invention.

FIG. 29 is a diagram for describing a structure of the main componentsof a flash memory device according to a ninth embodiment of the presentinvention.

FIG. 30 is a plan view of a semi-finished product for an integratedsemiconductor device according to a tenth embodiment of the presentinvention.

FIG. 31 is a diagram for showing in detail a semiconductor chip and adicing region of FIG. 30.

FIG. 32 is a diagram for describing the main component of asemi-finished product for an integrated semiconductor device accordingto an eleventh embodiment of the present invention.

FIG. 33 is a timing chart for describing a testing operation of thesemi-finished product for an integrated semiconductor device shown inFIG. 32.

FIG. 34 is a diagram for describing the main components of asemi-finished product for an integrated semiconductor device accordingto a twelfth embodiment of the present invention.

FIG. 35 is a timing chart for describing a testing operation of thesemi-finished product for an integrated semiconductor device of FIG. 34.

FIG. 36 is a block diagram showing a structure of the main components ofone semiconductor chip in a semi-finished product for an integratedsemiconductor device according to a thirteenth embodiment of the presentinvention.

FIG. 37 is a diagram for describing the main components of asemi-finished product for an integrated semiconductor device accordingto a fourteenth embodiment of the present invention.

FIG. 38 is a timing chart for describing a testing operation of thesemi-finished product for an integrated semiconductor device of FIG. 37.

FIG. 39 is a block diagram showing a structure of a row predecoder, aword driver, and a memory cell in a conventional DRAM.

FIG. 40 is a circuit diagram showing a specific structure of the rowpredecoder of FIG. 39.

FIG. 41 is a block diagram showing a structure of an DRAM shown in FIG.3 in "IEDM93, DIGEST" pp. 639-642.

FIG. 42 is a plan view of a semi-finished product for a conventionalintegrated semiconductor device having a plurality of semiconductorchips formed on a semiconductor wafer.

FIG. 43 is a plan view of a probe card for testing the semiconductorchips of FIG. 42 on a wafer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detailhereinafter with reference to the drawings. In the drawings,corresponding components have the same or likewise reference charactersallotted.

First Embodiment

Referring to FIG. 1, a DRAM of a first embodiment includes a memory cellarray 11, a row decoder 12, a column decoder 13, a sense amplifier train14, an input/output circuit 15, a row and column address buffer 16, aninput buffer 17, an output buffer 18, a clock generation circuit 19, amulti-selection pad 20, and a multi-selection signal generation circuit21. All the above circuit elements are formed on one semiconductorsubstrate 10.

FIG. 2 shows a partial structure of memory cell array 11, senseamplifier train 14, and input/output circuit 15. Memory cell array 11includes a plurality of word lines WL arranged in a row direction, aplurality of bit line pairs BL and /BL arranged in a column direction,and a plurality of dynamic memory cells 111 provided corresponding torespective crossings of word line WL and a bit line pair BL and /BL. Abit line pair is formed of a bit line BL and a complementary bit line/BL. FIG. 3 is a circuit diagram of memory cell array 11 in a simplifiedmanner wherein the pair of bit line BL and /BL are indicated by oneline.

FIG. 4 is a sectional view of one dynamic memory cell 111 formed on a ptype semiconductor substrate 10. Referring to FIGS. 2-4, dynamic memorycell 111 includes one access transistor 112 and one cell capacitor 113.Access transistor 112 is connected between a corresponding bit line BLor /BL and capacitor 113. Access transistor 112 has its gate electrodeconnected to a corresponding word line. As shown in FIG. 4, accesstransistor 112 includes n⁺ source/drain regions 1121 and 1122 formed onp type semiconductor substrate 10, and a gate electrode forming wordline WL on semiconductor substrate 10 with gate oxide film 1123therebetween. Bit line BL is in contact with one source/drain region1121 of access transistor 112. Cell capacitor 113 includes a storagenode 114, and a cell plate 115 formed on storage node 114 with adielectric film 116 therebetween. Storage node 114 forms contact withthe other source/drain region 1122 of access transistor 112.

Referring to FIG. 2 again, sense amplifier train 14 of FIG. 1 includes aplurality of sense amplifiers 141. Sense amplifiers 141 are providedcorresponding to bit line pairs BL and /BL. Each sense amplifier 141 isconnected to a corresponding bit line pair to amplify the potentialdifferential of the bit lines BL and /BL.

The DRAM further includes a bit line precharge potential generator 22for generating a predetermined bit line precharge potential VBL, and aplurality of bit line equalize circuits 23. Bit line equalize circuits23 are provided corresponding to bit line pairs BL and /BL. Each bitline equalize circuit 23 is connected to a corresponding bit line pairto equalize the potential of the relevant bit lines BL and /BL, andsupplies bit line precharge potential VBL from bit line prechargepotential generator 22 to the corresponding bit lines BL and /BL. Apotential of 1/2 the power supply potential VCC, for example (referredto as "intermediate potential VCC/2" hereinafter) is used as bit lineprecharge potential VBL. Each bit line equalize circuit 23 includes an Nequalize channel MOS transistor 231 connected between corresponding bitlines BL and /BL, and precharge N channel MOS transistors 232 and 233,each connected between bit line precharge potential generator 22 andrespective bit lines BL and /BL. Transistors 231-233 are turned onsimultaneously in response to an equalize signal EQ provided at apredetermined timing. Therefore, bit lines BL and /BL are equalized bytransistor 231, and precharged to the level of bit line prechargepotential VBL by transistors 232 and 233.

Input/output circuit 15 includes a pair of input/output lines IO and /IOand a plurality of column select gates 151 and 152. Column select gates151 and 152 are provided corresponding to bit line pairs BL and /BL.Each column select gate 151 is connected between a corresponding bitline BL and one input/output line IO. Each column select gate 152 isconnected between a corresponding bit line BL and the other input/outputline IO. Column select gates 151 and 152 are turned on in response to acolumn select signal CS applied from column decoder 13 shown in FIG. 1.

Referring to FIG. 1 again, clock generation circuit 19 responds toexternally applied external row address strobe signal /RAS and externalcolumn address strobe signal /CAS to generate a control signal such asan internal row address strobe signal and an internal column addressstrobe signal. Row and column address buffer 16 responds to an internalrow address strobe signal from clock generation circuit 19 to allowentry of address signals A1-An to provide a row address signal and acomplementary row address signal to row decoder 12. Row and columnaddress buffer 16 further responds to an internal column address strobesignal from clock generation circuit 19 to allow entry of addresssignals A1-An to provide a column address signal and a complementarycolumn address signal to column decoder 13.

This DRAM includes a normal mode and a test mode. In a normal mode, nopotential is applied to multi-selection pad 20. Therefore,multi-selection pad 20 attains an electrically floating state.Multi-selection signal generation circuit 21 generates a multi-selectionsignal MLT of an L level when multi-selection pad 20 attains a floatingstate. In a test mode, ground potential GND, for example, is supplied tomulti-selection pad 20. Multi-selection signal generation circuit 21generates a multi-selection signal MLT of an H level when the potentialof multi-selection pad 20 attains the level of ground potential GND.Thus, multi-selection signal MLT attains an L level in a normal mode andat H level in a test mode.

Multi-selection signal MLT is applied to row decoder 12. When amulti-selection signal MLT of an L level is provided, row decoder 12carries out a normal operation identical to that of a general case. Morespecifically, row decoder 12 responds to a row address signal toselectively drive one word line in memory cell array 11. As a result,data is readout to bit line pair BL and /BL from all the memory cells111 connected to the driven word line WL in a readout operation. Datareadout causes the potential difference between bit lines BL and /BL tobe amplified by sense amplifier 141, whereby the potential of one of bitlines BL and /BL is amplified to an H level, and the potential of theother bit line /BL or BL is amplified to the L level. Column decoder 13responds to a column address signal to select one bit line pair BL andBL. More specifically, one column select signal CS attains an H level,whereby corresponding column select gates 151 and 152 are turned on.Therefore, the amplified data on corresponding bit lines BL and /BL isapplied to input buffer 18 via input/output data line pair IO and IO.Output buffer 18 responds to output enable signal /OE to provide thedata as input/output data DQ1-DQ4. In a writing operation, input buffer17 responds to a write enable signal /WE to supply input/output dataDQ1-DQ4 to input/output circuit 15.

When a multi-selection signal MLT of an H level is provided, row decoder12 selectively drives all word lines WL in memory cell array 11.Therefore, all the word lines WL are activated in a test mode, whereby atest-stress is applied to access transistor 112 in all memory cells 111.

The structure of multi-selection signal generation circuit 21 and rowdecoder 12 characteristic of the first embodiment will be described indetail hereinafter.

Referring to FIG. 5, multi-selection signal generation circuit 21includes P channel MOS transistors 211 and 212 connected in parallelbetween a power supply node to which power supply potential VCC isapplied and multi-selection pad 20, and a P channel MOS transistor 213and an N channel MOS transistor 214 forming an CMOS inverter. Sincetransistor 211 has its gate electrode supplied with ground potential,transistor 211 supplies a slight current Ic for compensating for thepotential of the node of multi-selection pad 20. The inverter formed oftransistors 213 and 214 inverts the logic level of the signal ofmulti-selection pad 20 to supply multi-selection signal MLT.Multi-selection signal MLT is fed back to the gate electrode oftransistor 212.

Although no potential is supplied to multi-selection pad 20 in a normalmode, the node of multi-selection pad 20 is slightly pulled up to an Hlevel since a slight current Ic is supplied thereto by transistor 211. Apotential of an L level is applied to the gate electrode of transistor212, whereby transistor 212 is turned on. As a result, the node ofmulti-selection pad 20 is strongly pulled up to an H level. Thus,multi-selection signal MLT generated by multi-selection signalgeneration circuit 21 is fixed at an L level.

In a test mode, ground potential GND is applied to multi-selection pad20, so that transistor 212 is turned on. Therefore, multi-selectionsignal MLT attains an H level.

Referring to FIG. 6, row decoder 12 includes a row predecoder 121responsive to row address signals RA1, /RA1-RA4, /RA4 for generatingpredecode signals X1-X8, a predecode signal line 122 supplied withpredecode signals X1-X8, a plurality of row decoder units RD1-RDnresponsive to row address signals RA5, /RA5-RA8, /RA8 for generatingdecode signals D1-Dn, and a plurality of word drivers WD11-WD14,WD21-WD24, and Wdn1-Wdn4 responsive to predecode signals X1-X8 anddecode signals D1-Dn to drive word line WL. Each word driver is formedof a 3-input AND gate to drive a corresponding word line WL in responseto one of decode signals D1-Dn, one of predecode signals X1-X4, and oneof predecode signals X5-X8.

In a normal mode, a multi-selection signal MLT of an L level is providedto row predecoder 121. In this case, row predecoder 121 responds to rowaddress signals RA1, /RA1, RA2, /RA2 to activate one of predecodesignals X1-X4 to an H level, and responds to row address signals RA3,/RA3, RA4, /RA4 to activate one of predecode signals X5-X8 to an Hlevel. In a test mode, a multi-selection signal MLT of an H level issupplied to row predecoder 121. In this case, row predecoder 121activates all predecode signals X1-X8 to an H level independent of rowaddress signals RA1, /RA1-RA4, /RA4.

Each of row decoder units RD1-Rdn is provided corresponding to four ofword drivers WD11-WD14, WF21-WD24, and Wdn1-Wdn4. For example, rowdecoder unit RD1 is provided corresponding to word drivers WD11-WD14.Row decoder unit RD2 is provided corresponding to word driversWD21-WD24. Row decoder unit RDn is provided corresponding to worddrivers WDn1-WDn4.

In a normal mode, a multi-selection signal MLT of an L level is providedto row decoder units RD1-Rdn. In this case, row decoder units RD1-Rdnrespond to row address signals RA5, /RA5-RA8, /RA8 to activate any ofdecode signals D1-Dn to an H level. For example, when row addresssignals /RA5 and /RA6 both attain an H level, row decoder unit RD1activates corresponding decode signal D1 to an H level. Row decoder unitRD2 is maintained at an L level. Therefore, only word drivers WD11-WD14that receive a decode signal D1 of an H level attains an active state.Furthermore, when only predecode signals X1 and X5 are activated to an Hlevel, only word driver WD11 is activated, and only a corresponding wordline WL is driven. Although predecode signals X1 and X5 of an H levelare applied to word driver WD21, word driver WD21 is not activated sincea corresponding decode signals D2 attains an L level.

In a test mode, multi-selection signal MLT of an H level is applied torow decoder unit RD1-RDn. In this case, row decoder units RD1-RDnactivate all decode signals D1-Dn to an H level. Since decode signalsD1-Dn of an H level are applied to all word drivers WD11-WD14,WD21-WD24, and WDn1-WDn4, all word drivers attain a state that allow aactivation. Since all predecode signals X1-X8 are activated to an Hlevel in a test mode, all word drivers are activated. Therefore, all theword lines WL are driven.

FIG. 7 is a block diagram showing a specific structure of row predecoder121, predecode signal lines 122 and one word driver WDij together withcorresponding word line WL and memory cell 111. Word driver WDij of FIG.7 has a structure substantially identical to the conventional worddriver WD shown in FIG. 39. The decode system for selecting word driverWDij has a structure substantially equal to the conventional one in FIG.39. More specifically, word driver WDij includes N channel MOStransistors 123-125 connected in series between a precharge node NX anda ground node, a P channel MOS transistors 126 and 127 connected inparallel between a boosted power supply node to which a boostedpotential VPP is supplied and a precharge node NX, and a P channel MOStransistor 128 and N channel MOS transistor 129 forming an CMOSinverter. N channel MOS transistor 123 has its gate electrode suppliedwith a decode signal Di from a corresponding row decode unit. N channelMOS transistor 124 has its gate electrode supplied with one of predecodesignals X1-X4 as a predecode signal DECA. N channel MOS transister 125has its gate electrode supplied with one of predecode signals X5-X8 as apredecode signal DECB. P channel MOS transistor 126 responds to aprecharge signal PR to be turned on or off. The output signal of aninverter formed of transistors 128 and 129 is supplied to the gateelectrode of P channel MOS transistor 127. Word driver WDij responds todecode signal Di and predecode signals DECA and DECB to be selectivelyactivated. In an inactive state, precharge signal PR of an L level isapplied to the gate electrode of transistor 126. Therefore, thepotential of precharge node NX is weakly pulled up to the level ofboosted potential VPP by transistor 126. Therefore, the inverter formedof transistors 128 and 129 supplies an output signal of an L level tothe gate electrode of transistor 127, whereby the potential of prechargenode NX is strongly pulled up to the level of boosted potential VPP.Therefore, the potential of a corresponding word line WL is fixed to anL level. When decode signal Di and predecode signals DECA and DECB allattain an H level, transistors 123-125 are all turned on, whereby thepotential of precharge node NX is discharged to the level of groundpotential. Transistor 129 is turned off and transistor 128 is turned on,whereby boosted potential VPP is supplied to a corresponding word lineWL.

Referring to FIG. 8, row predecoder 121 includes a plurality of NORgates 1211-1218 and 1221-1228, and a plurality of inverters 1231-1238.Each of NOR gates 1211-1214 receives a row address signal RA1 or /RA1and a row address signal RA2 or /RA2. For example, NOR gate 1211receives row address signals /RA1 and /RA2. Each of NOR gates 1215-1218receives a row address signal RA3 or /RA3, and a row address signal RA4or /RA4. For example, NOR gate 1215 receives row address signals /RA3and /RA4. Each of NOR gates 1221-1224 receives multi-selection signalMLT and an output signal of a corresponding NOR gate. For example, NORgate 1221 receives multi-selection signal MLT and an output signal ofNOR gate 1211. Each of NOR gate 1225-1228 receives a multi-selectionsignal MLT and an output signal of a corresponding NOR gate. Forexample, NOR gate 1225 receives multi-selection signal MLT and an outputsignal of NOR gate 1215. Inverters 1231-1238 invert respective outputsignals of NOR gates 1221-1228 to generate predecode signals X1-X8. Rowpredecoder 128 has a structure basically similar to that of theconventional row predecoder 121a shown in FIG. 4 provided that NOR gates1221-1228 are provided instead of inverters 1221a-1228a. NOR gates1221a-1228 receive one common multi-selection MLT. Since a commonmulti-selection signal MLT of an L level is supplied to NOR gates1221-1228 in a normal mode, NOR gates 1221-1228 function as an inverter.Therefore, row predecoder 128 operates in a conventional manner. In atest mode, multi-selection signal MLT of an H level is supplied to NORgates 1221-1228, so that each of NOR gates 1221-1228 generates outputsignal of an L level independent of row address signals RA1, /RA1-RA4,/RA4. In this case, all predecoder signals X1-X8 are activated to an Hlevel independent of row address signals RA1, /RA1-RA4, /RA4.

Referring to FIG. 9, each of row decode units RD1-RD8 includes two NORgates (1241-1248, 1251-1258) and one inverter (1261-1268). For example,row decoder unit RD1 includes NOR gates 1241, 1251 and an inverter 1261.Each of NOR gates 1241-1248 receives a row address signal RA5 or /RA5,and a row address signal RA6 or /RA6. Each of NOR gates 1251-1258receives multi-selection signal MLT and an output signal of acorresponding NOR gate. For example, NOR gate 1251 receivesmulti-selection signal MLT and an output signal of NOR gate 1241.Therefore, NOR gates 1251-1258 receive in common one multi-selectionsignal MLT. Each of inverters 1261-1268 inverts an output signal of NORgate 1251 to generate a corresponding decode signal. For example,inverter 1261 inverts an output signal of NOR gate 1251 to generate acorresponding decode signal D1.

Since multi-selection signal MLT of an L level is applied to NOR gates1251-1258 in a normal mode, NOR gates 1251-1258 function as inverters.Therefore, only the row decoder unit to which row address signals ofboth the H level are supplied generates a decode signal of an H level.For example, when row address signals /RA5 and /RA6 both attain an Hlevel, row decoder unit RD1 generates a decode signal D1 of an H level,and other row decoder units RD2-RD4 generate respective decode signalsD2-D4 of an L level. When row address signals /RA7 and /RA8 both attainan H level, row decoder unit RD5 generates a decode signal D5 of an Hlevel, and other row decoder units RD6-RD8 generate respective decodesignals D6-D8 of an L level. In a test mode, multi-selection signal MLTof an H level is supplied to NOR gates 1251-1258, so that row decoderunits RD1-RD8 all generate respective decode signals D1-D8 of an H levelindependent of row address signals RA5, /RA5-RA8, /RA8.

An operation of the DRAM of the above-described structure will bedescribed hereinafter with reference to the timing chart of FIG. 10.

(1) Operation in Normal Mode

Since no potential is supplied to multi-selection pad 20 shown in FIG. 1in a normal mode, multi-selection signal generation circuit 21 generatesmulti-selection signal MLT of an L level. This multi-selection signalMLT is supplied to row predecoder 121 and row decoder units RD-RDn inrow decoder 12. The provision of a multi-selection signal MLT of an Llevel causes row predecoder 121 and row decoder units RD1-RDn to operatein a general manner. More specifically, row predecoder 121 responds torow address signals RA1, /RA1, RA2 and /RA2 to activate any of predecodesignals X1-X4 to an H level. Row predecoder 121 also responds to rowaddress signals RA3, /RA3, RA4, and /RA4 to activate any of predecodesignals X5-X8 to an H level.

In row decoder units RD1-RD8, any of decode signals D1-D8 is activatedto an H level in response to row address signals RA5, /RA5-RA8, /RA8. Asa result, four of word drivers WD11-WD14, WD21-WD24, and WDn1-WDn4 toattain a state that allows activation. Among these four word drivers,only the word driver receiving predecode signals of an H level isactivated. Therefore, only one word line WL in memory cell array 11 isdriven.

(2) Operation of Test Mode

In a test mode, ground potential GND is supplied to multi-selection pad20, whereby multi-selection signal generation circuit 21 provides amulti-selection signal MLT of an H level. This multi-selection signalMLT is applied to row predecoder 121 and row decoder units RD1-RDn inrow decoder 12. In response to multi-selection signal MLT of an H level,row predecoder 121 activates all predecode signals X1-X8 to an H levelirrespective of row address signals RA1, /RA1-RA4, /RA4. In response tomulti-selection signal MLT of an H level, row decoder units RD1-RD8activate all decode signals D1-D8 to an H level irrespective of rowaddress signals RA5, /RA5-RA8, /RA8. Therefore, all word driversWD11-WD14, WD21-WD24, and WDn1-WDn4 are activated, whereby all wordlines WL are driven.

The transition of multi-selection signal MLT to an H level from an Llevel shown in FIG. 10(c) causes all predecode signals X1-X8 to bepulled up to an H level from an L level as shown in FIG. 10(b)independent of row address signals RA1-RA8 shown in FIG. 10(a). Thepotential of all word lines is boosted to the level of boosted potentialVPP as shown in FIG. 10(d). Therefore, a high voltage is applied to gateoxide film 1123 of access transistor 112 shown in FIG. 4, whereby astress is applied on access transistor 112.

According to the first embodiment, all the word lines are activated atthe same time in a test mode. Therefore, the acceleration testing withrespect to an access transistor can be carried out in a short timeperiod. Furthermore, the above-described word line multi-selection canbe implemented with a simple structure since one multi-selection signalMLT is supplied to a row decoder 12 which drives all word lines WL in atest mode. More specifically, NOR gates 1221-1228 receiving onemulti-selection signal MLT in common are provided in row predecoder 121,and NOR gates 1251-1258 receiving one multi-selection signal MLT incommon are provided in row decoder units RD1-RD8. Thus, word linemulti-selection is possible in a test mode by slightly modifying thestructure of a conventional implement.

It is noted that NOR gates 1221-1228 and 1251-1258 can be formed withsufficient margin in contrast to the structure shown in FIG. 41 in whicha transistor is provided for multi-selection corresponding to each wordline. This margin is due to the great pitch of transistors in rowdecoder 12 in contrast to the extremely small pitch of the word lines.The possibility of these newly added NOR gates 1221-1228, 1251-1258being degraded or damaged is extremely small. The DRAM can be operatedstably. Furthermore, since power supply potential VCC is supplied withno provision of a boosted potential such as an in the transistor 1 ofFIG. 41, there is almost no possibility of these NOR gates 1221-1228,1251-1258 being damaged.

Second Embodiment

In the structure of the previous first embodiment, it is possible toprovide a multi-selection signal MLT of an H level to row decoder 12,not continuously, but intermittently, in a test mode. More specifically,the provision of a multi-selection signal alternately driven to an H andan L level at a predetermined cycle causes an AC stress to be applied ona word line. An AC stress is an acceleration test that applies a stresson a word line intermittently by alternate active/inactive states of aword line. However, the activation of all word lines at the same time issignificantly time-consuming since each its word line has a parasiticcapacitance of a pF order. It was therefore difficult to effectivelycarry out an acceleration testing of an AC stress in the structure ofthe first embodiment.

FIG. 11 is a circuit diagram showing a specific structure of apredecoder of an DRAM according to a second embodiment of the presentinvention that can solve the above problem.

This row predecoder 123 is used instead of row predecoder 121 shown inFIGS. 26 and 27. Referring to FIG. 11, row predecoder 123 receives twomulti-selection signals MLT1 and MLT2 in contrast to row predecoder 121shown in FIG. 8. One multi-selection signal MLT1 is applied in common toNOR gates 1221-1222, 1225, and 1226. The other multi-selection signalMLT2 is applied in common to NOR gates 1223, 1224, 1227 and 1228.

FIG. 12 shows a circuit for generating multi-selection signals MLT1 andMLT2. Referring to FIG. 12, row predecoder 123 further includes anoscillator 124 responsive to multi-selection signal MLT applied frommulti-selection signal generation circuit 21 to generate amulti-selection signal MLT1 alternating between an H level and an Llevel, and an inverter 125 for inverting a generated multi-selectionsignal MLT1 to provide a multi-selection signal MLT2. Therefore, when amulti-selection signal MLT of an H level is provided to oscillator 124,a multi-selection signal MLT1 of a predetermined cycle is generatedtogether with a multi-selection signal MLT2 complementary tomulti-selection signal MLT1. Therefore, multi-selection signal MLT2attains an L level when multi-selection signal MLT1 attains an H level.Here, only predecode signals X1, X2, X5 and X6 attain an H level. Incontrast, multi-selection signal MLT2 attains an H level whenmulti-selection signal MLT1 attains an L level. In this case, onlypredecode signals X3, X4, X7 and X8 attain an H level.

A half of the word lines are activated in response to predecode signalsX1, X2, X5 and X6 of an H level, and the remaining half word lines aredriven in response to predecode signals X3, X4, X7, and X8 of an Hlevel. In the second embodiment, word lines WL are divided into twogroups of word lines. Therefore, the number of word lines driven at thesame time is reduced.

This means that the capacitance of the word lines that must becharged/discharged at the same time is reduced in comparison with thecase when all the word lines are alternately activated/inactivated. AnAC stress can be applied on word lines effectively.

Word lines WL1 and WL2 driven at the same time are preferably arrangedin an alternating manner as shown in FIG. 13. In FIG. 13, one half ofword lines WL1 forms one group, and the other half of word lines WL2forms the other group. For example, multi-selection signal MLT1 of an Hlevel causes the drive of only word line WL1, and multi-selection signalMLT2 of an H level causes the drive of only word line WL2.

When acceleration testing of the data holding characteristics of dynamicmemory cell 111 is carried out, desired data is written into memory cell111 of interest. Then, a corresponding bit line is intermittentlyamplified in a direction opposite to that of the data of the relevantmemory cell while the corresponding word line is still inactive. Forexample, when data of an H level is written into memory cell 111 ofinterest, the potential of the corresponding bit line is intermittentlyamplified to an L level. This induces leakage of data from memory cell111 to allow measurement of the time that memory cell 111 eventuallyeffects data error in an accelerated manner.

Acceleration testing can be carried out in a more severe condition. Inthis case, memory cell 111 of interest has a desired data writtentherein, and a memory cell 111 adjacent thereto has opposite datawritten therein. When the word line corresponding to the peripheralmemory cell 111 is driven intermittently, leakage from memory cell 111of interest to the peripheral memory cell 111 is accelerated. It ispossible to accelerate leakage towards a peripheral memory cell inaddition to leakage towards a bit line.

Since it is necessary to drive the word line intermittentlycorresponding to a peripheral memory cell in such an acceleration test,this testing will be time consuming in a structure such as that shown inthe first embodiment where all word lines are driven. In the presentsecond embodiments, two word lines adjacent to each other are drivenalternately. Therefore, acceleration testing of data leakage withrespect to a plurality of memory cells 111 can be carried outsimultaneously under such a severe status. Thus, the time required fortesting can be reduced significantly.

The present invention is not limited to the second embodiment in whichmulti-selection signals MLT1 and MLT2 are generated by oscillator 114,and multi-selection signals MLT1 and MLT2 may be provided from anexternal source instead of from oscillator 124. Since a row addresssignal is neglected in a test mode, a structure may be employed in whichmulti-selection signals MLT1 and MLT2 are selectively activated inresponse to a row address strobe signal /RAS.

Third Embodiment

A third embodiment of the present invention is directed to apply astress on a dielectric film 116 of cell capacitor 113 in addition to thestress applied on gate oxide film 1123 of access transistor 122 shown inFIG. 4.

FIG. 14 is a block diagram showing the main components of a DRAMaccording to the third embodiment. In addition to the structure of thefirst embodiment, the DRAM of the third embodiment further includes testpads 24 and 27, selectors 25 and 28, switching circuits 29 and 30, and acell plate potential generator 26. A desired bit line test potentialVBLT is applied to test pad 24. A desired cell plate test potential VCPTis applied to test pad 27. Selector 25 responds to bit line selectsignal SBL from switching circuit 29 to selectively supply bit lineprecharge potential VBL or bit line test potential VBLT to bit lineequalize circuit 23. Switching circuit 29 responds to row address strobesignal /RAS to supply bit select signal SBL to selector 25. In response,selector 25 is switched.

Cell plate potential generator 26 generates a predetermined cell platepotential VCP (for example, intermediate potential VCC/2). Selector 28responds to a cell plate select signal SCP from switching circuit 30 toselectively supply cell plate potential VCP or cell plate test potentialVCPT to a cell plate 115 of memory cell 111. Switching circuit 30responds to row address strobe signal /RAS to supply cell plate selectsignal SCP to selector 28. In response, selector 28 is switched.

In a normal mode, multi-selection signal MLT of an L level is applied toswitching circuits 29 and 30. Switching circuit 29 controls selector 25so as to select bit line precharge potential VBL independent of rowaddress strobe signal /RAS. Therefore, bit line precharge potential VBLgenerated by precharge potential generator 22 is provided to storagenode 114 of capacitor 113 via selector 25, bit line equalize circuit 23,bit line BL and access transistor 112. Switching circuit 30 controlsselector 28 so as to select cell plate potential VCP. Therefore, cellplate potential VCP generated by cell plate potential generator 26 isprovided to cell plate 115 of cell capacitor 113 via selector 28. Inthis case, the DRAM carries out a normal operation.

When multi-selection signal MLT is pulled up to an H level from an Llevel as shown in FIG. 15(d), switching circuit 29 responds to rowaddress strobe signal /RAS to control selector 25 so as to select bitline precharge potential VBL or bit line test potential VBLT. When rowaddress strobe signal /RAS attains an L level, for example, bit linetest potential VBLT supplied to test pad 24 is selected. As a result,bit line test potential VBLT is supplied to storage node 114 of cellcapacitor 113 via selector 25, bit line equalize circuit 23, bit line BLand access transistor 112. Switching circuit 30 responds to row addressstrobe signal /RAS to control selector 28 so as to select cell platepotential VCP or cell plate test potential VCPT. When row address strobesignal /RAS attains an L level, for example, cell plate test potentialVCPT supplied to test pad 27 is selected. As a result, cell plate testpotential VCPT is supplied to cell plate 115 of capacitor 113 viaselector 28.

Row address strobe signal /RAS is used to control the switching ofselectors 25 and 28 since all the word lines are driven independent ofthe row address signal in a test mode.

The method of applying a stress voltage to cell capacitor 113 includes amethod of applying a high potential to storage node 114 and a lowpotential to cell capacitor 115, and a method of supplying a lowpotential to storage node 114 and a high potential to cell plate 115.

According to the third embodiment, a desired bit line test potentialVBLT and a desired cell plate test potential VCPT can be applied to testpads 24 and 27, respectively. Therefore, a desired stress voltage can beapplied to cell capacitor 113. The possibility of cell capacitor 113being damaged due to the application of a stress voltage higher than thepower supply potential can be eliminated according to the thirdembodiment in which the lowest required stress voltage of a level thatdoes not damage cell capacitor 113 can be applied thereto.

The present invention is not limited to the third embodiment in whichrow address strobe signal /RAS for activating a chip in a normal mode isused as a switching signal for test potentials VBLT and VCPT, andanother control signal may be used instead of or in addition to rowaddress strobe signal /RAS.

Furthermore, an AC stress can be applied to cell capacitor 113 byapplying alternately cell plate test potential VCPT and bit line testpotential VBLT to test pads 24 and 27 that is altered periodicallybetween power supply potential VCC and ground GND as shown in (f) and(g) in FIG. 16. Alternate change in the polarity of the stress voltageon cell capacitor 113 causes a change in the gate-source voltage ofaccess transistor 112. Therefore, the stress between the gate and sourceof access transistor 112 is further accelerated.

Fourth Embodiment

Referring to FIG. 17, an DRAM of a fourth embodiment includes amulti-selection detection circuit 34. Multi-selection detection circuit34 generates a multi-selection MLT of an L level in a normal mode whichis provided to row decoder 12. Multi-selection detection circuit 34generates a multi-selection signal MLT of an H level which is suppliedto row decoder 12 when a super VCC higher than power supply potentialVCC is applied to an address terminal thereof at the timing of a WCBR(/WE, /CAS before /RAS).

/RAS buffer 31 responds to external row address strobe signal /RAS toprovide an internal row address strobe signal to multi-selectiondetection circuit 34. A /CAS buffer 32 responds to an external columnaddress strobe signal /CAS to provide an internal column address strobesignal to multi-selection detection circuit 34. A /WE buffer 33 respondsto an external write enable signal /WE to supply an internal writeenable signal to multi-selection detection circuit 34. An address buffer16 responds to an external address signal Ai to supply an internal rowaddress signal to row decoder 12. A sense amplifier control circuit 35controls a sense amplifier train 14 so as to amplify data from memorycell array 11.

FIG. 18 is a timing chart showing an operation of multi-selectiondetection circuit 34 of FIG. 17. Multi-selection detection circuit 34attains a state that allows input of an address key when write enablesignal /WE and column address strobe signal /CAS are both pulled downprior to the fall of row address strobe signal /RAS, i.e. when rowaddress strobe signal /RAS, column address strobe signal /CAS and writeenable signal /WE are applied in the timing of WCBR, as shown in (a)-(c)of FIG. 18. Then, when a super VCC higher than power supply potentialVCC is supplied to the address terminal to which address signal Ai is tobe applied as shown in (d), multi-selection detection circuit 34activates multi-selection signal MLT to an H level as shown in (e). Thismulti-selection signal MLT of an H level is supplied to row decoder 12,whereby row decoder 12 drives all the word lines in memory cell array11.

According to the fourth embodiment, multi-selection signal MLT isactivated when an address key of super VCC is input at the timing ofWCBR. Therefore, acceleration testing by such word line multi-selectioncan be carried out even after this DRAM is molded by resin and furtherpackaged.

Fifth Embodiment

Referring to FIG. 19, a DRAM of the fifth embodiment further comprises,in addition to the component shown in FIG. 17, AND circuits 36 providedcorresponding to memory cell array 11. Each AND gate 36 responds tomulti-selection signal MLT and an internal row address strobe signal tosupply an output signal thereof to a corresponding row decoder 12.

Therefore, even when an address key of super VCC is input at a WCBRtiming as shown in (a)-(d) of FIG. 20 to cause activation ofmulti-selection signal MLT as shown in (e), the potential of word lineWL is not immediately boosted as shown in (f). When multi-selectionsignal MLT is activated, and row address strobe signal /RAS is pulleddown as shown in (c), the potential of word line WL is boosted to thelevel of boosted potential VPP.

According to the fifth embodiment, all word lines WL can be driven inresponse to a row address strobe signal /RAS in a test mode. Therefore,acceleration testing of a memory cell can be carried out at a desiredtiming.

Sixth Embodiment

Referring to FIG. 21, an DRAM of the sixth embodiment includes selectors37 and 38 instead of selectors 25 and 28 shown in FIG. 14. Selector 37is connected to, in addition to bit line precharge potential generator22, a power supply node to which power supply potential VCC is supplied,and to a ground node to which ground potential GND is supplied. Selector38 is connected to, in addition to cell plate potential generator 26,the power supply node and the ground node. Therefore, selector 37responds to bit line select signal SBL from switching circuit 29 toselectively supply bit line precharge potential VBL, power supplypotential VCC, and ground potential GND to bit line equalize circuit 23.Switching circuit 29 responds to multi-selection signal MLT and rowaddress strobe signal /RAS to switch selector 37. A multi-selectionsignal MLT of an L level causes bit line precharge potential VBL to besupplied to bit line equalize circuit 23 independent of row addressstrobe signal /RAS. A multi-selection signal MLT of an H level and a rowaddress strobe signal /RAS of an H level causes power supply potentialVCC to be supplied to bit line equalize circuit 23. A multi-selectionsignal MLT of an H level and row address strobe signal /RAS of an Llevel causes ground potential GND to be supplied to bit line equalizecircuit 23.

Selector 38 responds to cell plate select signal SCP from switchingcircuit 30 to selectively provide cell plate potential VCP, groundpotential GND and power supply potential VCC to cell plate 115. Whenmulti-selection signal MLT attains an L level, cell plate potential VCPis supplied to cell plate 115 independent of row address strobe signal/RAS. When multi-selection signal MLT and row address strobe signal /RASboth attain an H level, ground potential GND is supplied to cell plate115. When multi-selection signal MLT attains an H level and addressstrobe signal /RAS attains an L level, power supply potential VCC issupplied to cell plate 115.

FIG. 22 shows a circuit diagram of a specific structure of switchingcircuits 29 and selector 37 of FIG. 21. Referring to FIG. 22, switchingcircuit 29 includes an inverter 291 receiving multi-selection signalMLT, an NOR gate 292 receiving an output signal of inverter 291 and rowaddress strobe signal /RAS, an AND gate 293 receiving multi-selectionsignal MLT and row address strobe signal /RAS, and an inverter 294receiving multi-selection signal MLT. Selector 37 includes inverters371, 372, 375, and transfer gates 372, 374, and 376.

When multi-selection signal MLT attains an H level, transfer gates 372is turned on, whereby selector 37 provides bit line precharge potentialVBL. When multi-selection signal MLT and row address strobe signal /RASattains an H level, transfer gates 374 is turned on, whereby selector 37provided power supply potential VCC. When multi-selection signal MLTattains an H level and row address strobe signal /RAS attains an Llevel, transfer gates 374 is turned on, whereby selector 37 providesground potential GND.

FIG. 23 is a circuit diagram showing a specific structure of switchingcircuit 30 and selector 38 of FIG. 21. Referring to FIG. 23, switchingcircuit 30 includes inverters 391 and 394, an NOR gate 392, and an ANDgate 393, similar to switching circuit 29 shown in FIG. 22. Selector 38includes inverters 381, 383, and 385, and transfer gates 382, 384 and386, similar to selector 37 shown in FIG. 22.

When multi-selection signal MLT attains an L level, selector 38 providescell plate potential VCP. When multi-selection signal MLT and rowaddress strobe signal /RAS attains an H level, selector 38 providesground potential GND. When multi-selection signal MLT attains an H leveland row address strobe signal /RAS attains an L level, selector 38provides power supply potential VCC.

In the sixth embodiment, the polarity of the stress voltage applied tocell capacitor 113 is switched in response to row address strobe signal/RAS. Therefore, an AC stress can be applied to cell capacitor 113.

Since selectors 37 and 38 are connected to the power supply node and theground node in the sixth embodiment, test pads 24 or 27 shown in FIG. 14are not required. In carrying out acceleration testing of the presentDRAM, the five potentials and signals of multi-selection signal MLT, rowaddress strobe signal /RAS, power supply potential VCC, ground potentialGND, and boosted voltage VPP for driving a word line are applied fromthe outside world. In an acceleration testing such as burn-in, powersupply potential VCC is set higher than that of a normal one. Therefore,power supply potential VCC may be directly supplied as boosted potentialVPP. In this case, acceleration testing can be carried out by providingfour signals and potentials from the outside world.

Recently, the tendency is to carry out stress testing in a wafer stateof chips of DRAMs prior to a dicing process. A procedure called paralleltesting that tests a plurality of chips at the same time on a waferduring stress testing is now often used. If the number of potentials andsignals that must be provided for such testing is great, a tester havinga greater number of pins is required, resulting in increase of the costfor testing. Even when testing is carried out using a probe card, thetesting cost is also increased since a complex probe card is necessaryhaving a great number of probes.

In contrast, the sixth embodiment allows stress testing by applyingsignals and potentials to a small number of pads such as four or fivepads. Therefore, the number of chips that can be tested simultaneouslyis increased, whereby the cost for testing is decreased.

Seventh Embodiment

Referring to FIG. 24, a DRAM according to a seventh embodiment of thepresent invention includes a power supply pad 39 receiving an externallyapplied power supply potential VCC, a ground pad 40 receiving anexternally applied ground potential GND, a multi-selection pad 41receiving an externally applied multi-selection signal MLT, and aboosted power supply pad 42 receiving an externally applied externalboosted potential VPPE. The DRAM further includes selectors 43, 44, and48, a logic level determination circuit 45, a VCC level determinationcircuit 46, and a boosted potential generator 47. Logic leveldetermination circuit 45 makes determination of an H level or an L levelof multi-selection signal MLT from multi-selection pad 41 to supply aselect signal SEL1 according to a determination result thereof toselectors 43 and 44. VCC level determination circuit 46 determineswhether multi-selection signal MLT from multi-selection pad 41 attainsthe level of power supply potential VCC or a higher super VCC level tosupply a select signal SEL2 according to the determination result toselectors 43 and 44. Therefore, a multi-selection signal MLT of an Hlevel having a level of super VCC higher than power supply potential VCCcan be provided in addition to the level of power supply potential VCC.VCC level determination circuit 46 includes 2 to 3 diode-connectedtransistors (not shown) connected in series, and can detect a super VCChigher than power supply potential VCC by the threshold voltage of thesetwo to three transistors.

Selector 43 responds to select signals SEL1 and SEL2 to select bit lineprecharge potential VBL from bit line precharge potential generator 22,power supply potential VCC from power supply pad 39, or ground potentialGND from ground pad 40 to supply the selected potential to the bit lineequalize circuit in memory cell array 11 as bit line potential VBL1.Selector 44 responds to select signals SEL1 and SEL2 to select cellplate potential VCP from cell plate potential generator 26, groundpotential VCC from power supply pad 39, or ground potential GND fromground pad 40 to supply the selected potential to the cell plate in amemory cell in memory cell array 11 as cell plate potential VCP1.

Boosted potential generator 47 generates an internal boosted potentialVPPI higher than power supply potential VCC according to power supplypotential VCC. Selector 48 selects an internal boosted potential VPPI orexternal boosted potential VPPE from boosted power supply pad 42 tosupply the selected potential to the word driver in row decoder 12.

In a normal mode, bit line precharge potential VBL is provided from bitline precharge potential generator 22 to a bit line via selector 43.Furthermore, cell plate potential VCP from cell plate potentialgenerator 26 is supplied to the cell plate via selector 44.

In a test mode, power supply potential VCC or super VCC is supplied tomulti-selection pad 41 as multi-selection signal MLT of an H level asshown in FIG. 25(c). Activation of multi-selection signal MLT to an Hlevel causes all predecode signals X1-X8 to be activated to an H levelas shown in FIG. 25(b), whereby the potential of all the word lines WLin memory cell array 11 is boosted to the level of boosted potential VPPas shown in FIG. 25(d).

When determination is made that multi-selection signal MLT attains an Hlevel by logic level determination circuit 45 and that the H levelmulti-selection signal MLT attains the level of power supply potentialVCC by VCC level determination circuit 46, selector 43 selects powersupply potential VCC, whereby the selected power supply potential VCC issupplied to a bit line as bit line potential VBL1 as shown in FIG.25(e). In this case, selector 44 selects ground potential GND, which issupplied to the cell plate as cell plate potential VCP1 as shown in FIG.25(f).

When determination is made that multi-selection signal MLT attains an Hlevel by logic level determination 45 and that the H levelmulti-selection signal MLT attains the level of super VCC level by VCClevel determination circuit 46, selector 43 selects ground potential GNDwhich is supplied to a bit line as bit line potential VBL1 as shown inFIG. 25(e). In this case, selector 44 selects power supply potentialVCC, which is supplied to the cell plate as cell plate potential VCP1 asshown in FIG. 25(f).

In contrast to internal boosted potential VPP1 generated by boostedpotential generator 47 supplied to row decoder 12 via selector 48 in anormal mode, the externally applied external boosted potential VPPE atboosted power supply pad 42 is supplied to row decoder 12 via selector48 in a test mode. According to the seventh embodiment, the plurality ofword lines WL driven in a test mode can be driven in a sufficient mannersince external boosted potential VPPE is supplied.

According to the seventh embodiment, multi-selection signal MLT can beapplied in three types of levels. Therefore, row address strobe signal/RAS to switch between power supply potential VCC and ground potentialGND as in FIG. 21 is not required. Switching between power supplypotential VCC and ground potential GND is possible according to twotypes of H levels of a multi-selection signal.

A stress can be applied to the DRAM of the seventh embodiment byproviding four potentials and signal of power potential VCC, groundpotential GND, multi-selection signal MLT, and external boostedpotential VPPE. In testing such an DRAM under a wafer state prior to adicing process, a signal and potential required for applying a stresscan be easily provided from the outside world. Therefore, the costrequired for testing can be reduced.

The present invention is not limited to the seventh embodiment in whichboosted potential VPPE for driving a word line is supplied from boostingpower supply pad 42, and power supply potential VCC supplied to powersupply pad 39 may be supplied to row decoder 12. This is because a powersupply potential VCC higher than a conventional one is supplied from theoutside world in a stress test such as burn-in. In this case, apotential or signal for testing is supplied to three pads 39-41.

FIG. 26 shows the arrangement of a semiconductor chip including suchthree pads in a wafer state. FIG. 26 shows a plurality of semiconductorchips 71 formed on a semiconductor wafer. Each semiconductor chip 71includes three pads 39, 40, and 49, and an internal timer 711.Multi-selection pad 49 of semiconductor chip 71 differs from themulti-selection pad shown in FIG. 24 in that a burn-in signal isprovided thereto. Internal timer 711 responds to a burn-in signal frommulti-selection pad 49 to generate a multi-selection signal MLT of apredetermined cycle. Since internal timer 711 is provided in eachsemiconductor chip 71, each semiconductor chip 71 can be testedindividually in response to a multi-selection signal MLT internallygenerated.

FIG. 27 is a plan view of a probe card for testing a plurality ofsemiconductor chips 71 of FIG. 26 in a wafer state. As shown in FIG. 27,this probe card 74 includes a plurality of openings 741, and a pluralityof probes 742 protruding into respective openings 741. Each opening 741is provided so as to expose underlying semiconductor chips 71. Threeprobes 742 are arranged at the periphery of opening 741 corresponding toone semiconductor chip 71.

These probes 742 form contact with pads 39, 40 and 46 to supply powerpotential VCC, ground potential GND, and a burn-in signal for testing toeach semiconductor chip 71. Since a plurality of openings 741 are formedin probe card 74, not only three semiconductor chips 71 arranged in onevertical row, but fifteen semiconductor chips 71 arranged in a matrixcan be tested at the same time.

Reduction in the number of applied potentials and signals required fortesting provides the advantage of allowing testing of a plurality ofsemiconductor chips in a wafer state simultaneously using probe card 74of a simple structure as such shown in FIG. 74.

Eighth Embodiment

Referring to FIG. 28, a DRAM of an eighth embodiment includes asubstrate potential generator 50 for generating a predeterminedsubstrate potential VBB, and a selector 51 responsive to multi-selectionsignal MLT for selecting substrate potential VBB or externally appliedsubstrate test potential VBBT to supply the selected potential tosemiconductor substrate 10.

In contrast to the third embodiment shown in FIG. 14 in which bit linetest potential VBLT is supplied to storage node 114 via bit line BL, thepresent eight embodiment 8 has substrate test potential VBBT supplied tostorage node 114 via semiconductor substrate 10 and source/drain region1122 of access transistor 112. In the eighth embodiment, substrate testpotential VBBT must be set higher than cell plate potential VCPT sincesemiconductor substrate 10 is of a P type conductivity and source/drainregion 112 is of an n⁺ type conductivity. In a test mode, cell platetest potential VCPT is supplied to cell plate 115, and substrate testpotential VBBT is supplied to storage node 114. Therefore, a stressvoltage can be applied to dielectric film 116 of cell capacitor 113.

In the eighth embodiment, a substrate test potential can be supplied tostorage node 114 of all cell capacitors 113 just by supplying thesubstrate test potential to one semiconductor substrate 10 in a testmode. Therefore, the structure of the eight embodiment is more simplethan that of the third embodiment shown in FIG. 14.

It is appreciated that the polarities of cell plate test potential VCPTand substrate test potential VBBT are set opposite when a p⁺source/drain region is formed in an n type semiconductor substrate.

Ninth Embodiment

FIG. 29 shows a structure of a flash memory device according to a ninthembodiment of the present invention. Referring to FIG. 29, a memory cellline of the flash memory device includes a plurality of word lines WL, aplurality of source lines 52 crossing word lines WL, and a plurality offloating gate type memory cells 53 provided corresponding to respectivecrossings of a word line and a source line. Each floating gate typememory cell 53 includes a drain region 531 and a source region 532formed in a semiconductor substrate 10, a gate electrode 533 connectedto a corresponding word line WL, and a floating gate 534 formed beneathgate electrode 533. Data is stored in memory cell 53 by the accumulationof charge in floating gate 534. Since floating gate 534 attains anelectrically floating state, the data therein will not be lost even whenthe power is turned off.

In a normal access operation, one word line WL is driven, whereby thedata in memory cell 53 is read out on source line 52.

In a test mode, a plurality of word lines WL are driven in response toone multi-selection signal, similar to the above-described embodiment. Ahigh potential is supplied to gate electrode 533 connected to the drivenword line WL. Therefore, a high potential is applied in a direction fromgate electrode 533 towards source region 532, whereby the charge infloating gate 534 is drawn out into source region 532. As a result, datain memory cell 53 is erased.

According to the ninth embodiment, a plurality of word lines WL aredriven in response to a multi-selection signal, so that data in allmemory cells within a desired area can be erased simultaneously. Thus,the time required for erasing can be reduced.

Tenth Embodiment

FIG. 30 is a plan view showing a structure of a semi-finished product oran integrated semiconductor device according to a tenth embodiment ofthe present invention. As shown in FIG. 30, a plurality of semiconductorchips 71 are formed on a semiconductor wafer 70. These semiconductorchips 71 are arranged in a matrix. Each semiconductor chip 71 isdisposed with a predetermined distance from an adjacent semiconductorchip 71. Therefore, a dicing region 72 is provided between thesesemiconductor chips 71. Semiconductor wafer 70 is divided into pluralityof semiconductor chips 71 by dicing region 72. In general, the width ofdicing region 72 is set to approximately 50-200 μm.

In the tenth embodiment, test interconnections 721-723 shown in FIG. 31are formed horizontally and vertically in such a dicing region 72. Testinterconnections 721 formed vertically and horizontally are connected toeach other and receive power supply potential VCC. The vertically andhorizontally formed test interconnections 722 are connected to eachother, and receive ground potential GND. Vertically and horizontallyformed test interconnections 723 are connected to each other, andreceive a multi-selection signal MLT.

By supplying power supply potential VCC, ground potential GND, andmulti-selection signal MLT to respective one of test interconnections721-723, the potentials and signal can be supplied to all semiconductorchips 71 on semiconductor wafer 70. This means that an acceleration teston all semiconductor chips 71 on semiconductor wafer 70 can be carriedout using a general probe card that supplies a potential and signal fortesting only to one semiconductor chip 71. It is needless to say thatthe probe card as shown in FIG. 73 may also be used.

Eleventh Embodiment

When a plurality of semiconductor chips 71 are connected in common bytest interconnections 721-723 as shown in FIG. 31, the number ofsemiconductor chips 71 connected to one probe of the probe card isincreased. As a result, the load capacitance becomes greater. This meansthat the rising time period and falling time period of the potential andsignal applied to semiconductor chip 71 via the test interconnectionbecomes longer. It is therefore difficult to carry out accelerationtesting while operating semiconductor chip 71 at high frequency.

According to the eleventh embodiment 11 shown in FIG. 32, eachsemiconductor chip 71 includes an internal timer 711. The vertically andhorizontally formed test interconnections 724 are connected to eachother, and receive a burned-in signal BI. Burn-in signal BI is appliedto internal timer 711 of all semiconductor chips 71 on semiconductorwafer 70 via test interconnection 724.

Internal timer 711 operates automatically at the rise of burn-in signalBI as shown in FIG. 33(a), whereby a multi-selection signal MLT isgenerated periodically as shown in FIG. 33(b). This multi-selectionsignal MLT is applied to a row decoder, whereby a plurality of wordlines are activated. As shown in FIG. 33(c), the potential of word lineWL responds to multi-selection signal MLT to be pulled up and downalternately. Therefore, the potential of bit lines BL and /BL areamplified between the level of ground potential GND and power supplypotential VCC.

Since multi-selection signal MLT is generated by internal timer 711provided in each semiconductor chip 71 in the present eleventhembodiment, and an AC stress test can be carried out in an acceleratedmanner while operating each semiconductor chip 71 at high frequency.

Twelfth Embodiment

In the eleventh embodiment shown in FIG. 32, the variation in theoscillation frequency of internal timer 711 will cause a differentacceleration ratio of testing for each semiconductor chip since amulti-selection signal MLT of a predetermined frequency is generated byeach semiconductor chip 71.

In the present twelfth embodiment shown in FIG. 34, each semiconductorchip 71 includes a 1/n frequency divider 712. Vertically andhorizontally formed test interconnections 725 are connected to eachother, and receive an external clock signal CK. External clock signal CKis applied to frequency divider 712 of all semiconductor chips 71 on thesemiconductor wafer via test interconnection 725. Each frequency divider712 divides an applied external clock signal CK to generate amulti-selection signal MLT having a period of 1/n that of external clocksignal CK. For example, when n=2, the period of multi-selection signalMLT shown in FIG. 35(c) is half that of external clock signal CK shownin FIG. 35(b).

Therefore, the rising and falling time period of multi-selection signalMLT is 1/n that of external clock signal CK even if the rising andfalling time period of the supplied external clock signal CK is great.For example, when n=16, the period of multi-selection signal MLT is 100ns when the period of external clock signal CK is 1600 ns. Therefore,the rising and falling time period of multi-selection signal MLT is notmore than 5 ns even if the rising and falling time period ofmulti-selection signal MLT is approximately 50 ns. Since the rising andfalling time period can be reduced, an acceleration test can be carriedout while operating semiconductor chip 71 at a high frequency.Furthermore, the acceleration ratio in an acceleration test can be setsubstantially equal in each semiconductor chip 71 since frequencydivider 712 generates multi-selection signal MLT with external clocksignal CK as a trigger.

Thirteenth Embodiment

In the eleventh embodiment shown in FIG. 32, internal timer 711 fortesting is provided. When this semiconductor chip is a DRAM, the refreshtimer used for self refresh can be used as the internal timer in a testmode. A circuit for this purpose is shown in FIG. 36.

According to the thirteenth embodiment shown in FIG. 36, an outputsignal of an OR gate 713 receiving self refresh signal SREF and burn-insignal BI is applied to a refresh timer 714. An output signal of refreshtimer 714 and burn-in signal BI are applied to AND gate 715. Burn-in BIand external row address strobe signal /RASE are applied to an NOR gate716. A multiplexer 717 responds to a burn-in BI to select an outputsignal of AND gate 715 or NOR gate 716 to provide a selected signal atinternal row strobe signal /RASI.

In a self refresh mode, a burn-in signal BI of an L level is applied toactivate refresh timer 714. In response to an output signal of refreshtimer 714, an address counter 718 generates an internal address for aself refresh operation. A self refresh control circuit 719 responds tothe generated internal address to control a row decoder, a senseamplifier, and the like that sequentially refreshes the memory cell.

Furthermore, multiplexer 714 responds to burn-in signal BI of an L levelto select an output signal of NOR gate 716, whereby external row addressstrobe signal /RASE is output as internal row address strobe signal/RASI.

In a test node, burn-in signal BI of an H level is applied, so thatmultiplexer 717 selects an output signal of AND gate 715. Therefore, anoutput signal of refresh timer 714 is provided as internal row addressstrobe signal /RASI. In a test mode, a plurality of word lines areactivated periodically in response to this internal row address strobesignal /RASI. Therefore, an AC stress test of a memory cell can becarried out.

Since refresh timer 714 is used as an internal timer required in eachsemiconductor chip in the thirteenth embodiment, the region occupied bythe circuitry exclusively for acceleration testing can be reduced.

Fourteenth Embodiment

In the above-described embodiment, all word lines WE in a memory cellarray are activated in response to multi-selection signal MLT.Therefore, a great amount of power is consumed simultaneously when theword lines are charged/discharged. The present fourteenth embodimentshows a structure in which a plurality of word lines specified by anaddress can be sequentially activated.

Referring to FIG. 37 of a fourteenth embodiment, an address counter 718sequentially generates an internal address in response to an output ofinternal timer 711. Upon activation of multi-selection signal MLT asshown in FIG. 38(b), the potential of a plurality of word lines WL areraised to the level of boosted potential VPP as shown in FIG. 38(b)according to an internal address of address counter 718 as shown in FIG.38(d). At the next activation of multi-selection signal MLT, a pluralityof word lines WL are driven according to the next internal address.

Here, it is desirable to use the refresh timer of the self refreshoperation for internal timer 711 and the address counter of the selfrefresh operation for address counter 718. This is to reduce the areaoccupied by the circuitry required for acceleration testing.

According to the fourteenth embodiment, only a part of the word lines ina memory cell array are driven according to an internal address fromaddress counter 718. Therefore, the power consumed simultaneously forcharging/discharging word-lines is reduced. Furthermore, since anaddress for specifying a word line to be driven is internally generatedby address counter 718, such an address does not have to be providedfrom an external source. Therefore, the number of externally appliedpotentials and signals for testing can be reduced. Acceleration test canbe carried out easily under a wafer state.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A semiconductor memory device including a normalmode and a test mode, said semiconductor device comprising:a pluralityof word lines; a plurality of bit lines crossing said word lines; aplurality of memory cells provided corresponding to respective crossingsof said word lines and said bit lines, each memory cell connected to acorresponding word line and bit line; a plurality of drive meansprovided corresponding to said word line, each drive means for driving acorresponding word line; activation means responsive to an externallyapplied row address signal in said normal mode for selectivelyactivating one of said drive means, and responsive to a predeterminedmulti-selection signal in said test mode for activating at least two ofsaid drive means independent of said row address signal; and controlmeans responsive to an externally applied control signal and saidmulti-selection signal in said test mode for controlling said activationmeans to activate at least two of said drive means independent of saidrow address signal.
 2. A semiconductor memory device including a normalmode and a test mode, said semiconductor device comprising:a pluralityof word lines; a plurality of bit lines crossing said word lines; aplurality of memory cells provided corresponding to respective crossingsof said word lines and said bit lines, each memory cell connected to acorresponding word line and bit line; a plurality of drive meansprovided corresponding to said word line, each drive means for driving acorresponding word line; and activation means responsive to anexternally applied row address signal in said normal mode forselectively activating one of said drive means, and responsive to apredetermined multi-selection signal in said test mode for activating atleast two of said drive means independent of said row address signal,said activation means comprisinga predecoder for activating anypredecode signal by predecoding said row address signal in said normalmode, and for activating all said predecode signal in response to saidmulti-selection signal in said test mode, and a plurality of predecodesignal lines connected to said predecoder for receiving said pluralityof predecode signal, respectively, wherein each of said drive meanscomprises a word driver connected to any of said predecode signal linesfor driving a corresponding word line in response to a predecode signalof a predecode signal line connected thereto.
 3. The semiconductormemory device according to claim 2, wherein said predecoder comprisesaplurality of first logic gates, each receiving one of said row addresssignal and the complementary row address signal, and a plurality ofsecond logic gates provided corresponding to said first logic gates,each second logic gate receiving said multi-selection signal and anoutput signal of a corresponding first logic gate for providing acorresponding predecode signal.
 4. A semiconductor memory deviceincluding a normal mode and a test mode, said semiconductor devicecomprising:a plurality of word lines; a plurality of bit lines crossingsaid word lines; a plurality of memory cells provided corresponding torespective crossings of said word lines and said bit lines, each memorycell connected to a corresponding word line and bit line; a plurality ofdrive means provided corresponding to said word line, each drive meansfor driving a corresponding word line; activation means responsive to anexternally applied row address signal in said normal mode forselectively activating one of said drive means, and responsive to apredetermined multi-selection signal in said test mode for activating atleast two of said drive means independent of said row address signal;precharge potential generation means for generating a prechargepotential for said bit line; and a first potential supply means forsupplying said precharge potential from said precharge potentialgeneration means to said bit line when a first control signal isinactive, and for supplying a predetermined first test potential to saidbit line in response to an externally applied second control signal whensaid first control signal is active.
 5. A semiconductor memory deviceincluding a normal mode and a test mode, said semiconductor devicecomprising:a plurality of word lines; a plurality of bit lines crossingsaid word lines; a plurality of memory cells provided corresponding torespective crossings of said word lines and said bit lines, each memorycell connected to a corresponding word line and bit line; a plurality ofdrive means provided corresponding to said word line, each drive meansfor driving a corresponding word line; activation means responsive to anexternally applied row address signal in said normal mode forselectively activating one of said drive means, and responsive to apredetermined multi-selection signal in said test mode for activating atleast two of said drive means independent of said row address signal;precharge potential generation means for generating a prechargepotential for said bit line; and first potential supply means forsupplying said precharge potential from said precharge potentialgeneration means to said bit line when said multi-selection signal isinactive, and for supplying a predetermined first test potential to saidbit line in response to an externally applied control signal when saidmulti-selection signal is active.
 6. The semiconductor memory deviceaccording to claim 5, further comprising a first test pad externallyreceiving said first test potential.
 7. The semiconductor memory deviceaccording to claim 5, further comprising:cell plate potential generationmeans for generating a cell plate potential for a cell plate of saidmemory cell, and second potential supply means for supplying said cellplate potential to a cell plate of said memory cell from said cell platepotential generation means when said multi-selection signal is inactive,and for supplying a predetermined second test potential different fromsaid first test potential to a cell plate of said memory cell inresponse to said control signal when said multi-selection signal isactive.
 8. The semiconductor memory device according to claim 7, whereinsaid first potential supply means supplies said first test potential tosaid bit line when said control signal attains a first logic level, andsupplies a predetermined third test potential equal to said second testpotential to said bit line when said control signal attains a secondlogic level upon activation of said multi-selection signal,wherein saidsecond potential supply means supplies said second test potential to acell plate of said memory cell when said control signal attains thefirst logic level, and for supplying a predetermined fourth testpotential equal to said first test potential to a cell plate of saidmemory cell when said control signal attains the second logic level uponactivation of said multi-selection signal.
 9. A semiconductor memorydevice including a normal mode and a test mode, said semiconductordevice comprising:a plurality of word lines; a plurality of bit linescrossing said word lines; a plurality of memory cells providedcorresponding to respective crossings of said word lines and said bitlines, each memory cell connected to a corresponding word line and bitline; a plurality of drive means provided corresponding to said wordline, each drive means for driving a corresponding word line; activationmeans responsive to an externally applied row address signal in saidnormal mode for selectively activating one of said drive means, andresponsive to a predetermined multi-selection signal in said test modefor activating at least two of said drive means independent of said rowaddress signal; cell plate potential generation means for generating acell plate potential for a cell plate of said memory cell; and secondpotential supply means for supplying said cell plate potential from saidcell plate potential generation means to a cell plate of said memorycell when said multi-selection signal is inactive, and for supplying apredetermined second test potential to a cell plate of said memory cellin response to an externally applied control signal when saidmulti-selection signal is active.
 10. The semiconductor memory deviceaccording to claim 9, further comprising a second test pad externallyreceiving said second test potential.
 11. A semiconductor memory deviceincluding a normal mode and a test mode, said semiconductor devicecomprising:a plurality of word lines; a plurality of bit lines crossingsaid word lines; a plurality of memory cells provided corresponding torespective crossings of said word lines and said bit lines, each memorycell connected to a corresponding word line and bit line; a plurality ofdrive means provided corresponding to said word line, each drive meansfor driving a corresponding word line; activation means responsive to anexternally applied row address signal in said normal mode forselectively activating one of said drive means, and responsive to apredetermined multi-selection signal in said test mode for activating atleast two of said drive means independent of said row address signal;and multi-selection signal generation means responsive to apredetermined timing of externally applied plurality of control signalsfor generating said multi-selection signal.
 12. A semiconductor memorydevice including a normal mode and a test mode, said semiconductordevice comprising:a plurality of word lines; a plurality of bit linescrossing said word lines; a plurality of memory cells providedcorresponding to respective crossings of said word lines and said bitlines, each memory cell connected to a corresponding word line and bitline; a plurality of drive means provided corresponding to said wordline, each drive means for driving a corresponding word line; activationmeans responsive to an externally applied row address signal in saidnormal mode for selectively activating one of said drive means, andresponsive to a predetermined multi-selection signal in said test modefor activating at least two of said drive means independent of said rowaddress signal; and a multi-selection pad externally receiving saidmulti-selection signal.
 13. The semiconductor memory device according toclaim 12, further comprising:level determination means for determiningwhether said multi-selection signal applied to said multi-selection padattains a first level, a second level higher than said first level, or athird level higher than said second level, precharge potentialgeneration means for generating a precharge potential for said bit line,a first potential supply means for supplying said precharge potentialfrom said precharge potential generation means to said bit line whendetermination is made by said level determination means that saidmulti-selection signal attains to said first level, for supplying apredetermined first test potential to said bit line when determinationis made by said level determination means that multi-selection signalattains said second level, and for supplying a predetermined second testpotential to said bit line when determination is made by said leveldetermination means that said multi-selection signal attains said thirdlevel, cell plate potential generation means for generating a cell platepotential for a cell plate of said memory cell, and second potentialsupply means for supplying said cell plate potential from said cellplate potential generation means to a cell plate of said memory cellwhen determination is made by said level determination means that saidmulti-selection signal attains said first level, for supplying saidsecond test potential to a cell plate of said memory cell whendetermination is made by said level determination means that saidmulti-selection signal attains said second level, and for supplying saidfirst test potential to a cell plate of said memory cell whendetermination is made by said level determination means that saidmulti-selection signal attains said third level.
 14. A semiconductormemory device including a normal mode and a test mode, saidsemiconductor device comprising:a plurality of word lines; a pluralityof bit lines crossing said word lines; a plurality of memory cellsprovided corresponding to respective crossings of said word lines andsaid bit lines, each memory cell connected to a corresponding word lineand bit line; a plurality of drive means provided corresponding to saidword line, each drive means for driving a corresponding word line;activation means responsive to an externally applied row address signalin said normal mode for selectively activating one of said drive means,and responsive to a predetermined multi-selection signal in said testmode for activating at least two of said drive means independent of saidrow address signal; boosted potential generation means for generating aninternal boosted potential higher than a power supply potential; andword line drive potential supply means responsive to saidmulti-selection signal for selectively supplying said internal boostedpotential from said boosted potential generation means and apredetermined test potential to said drive means, wherein each of saiddrive means provides the supplied potential to said corresponding wordline to drive said corresponding word line.
 15. The semiconductor memorydevice according to claim 14, further comprising boosted power supplypad connected to said word line drive potential supply means to receiveexternal boosted potential equal to said internal boosted potential assaid test potential.
 16. The semiconductor memory device according toclaim 14, wherein said word line drive potential supply means suppliessaid power supply potential to said drive means as said test potential.17. A semiconductor memory device including a normal mode and a testmode, said semiconductor memory device comprising:a plurality of wordline groups, each including a plurality of word lines, a plurality ofbit lines crossing said word lines, a plurality of memory cells providedcorresponding to respective crossings of said word lines and said bitlines, each memory cell connected to a corresponding word line and bitline, a plurality of drive means provided corresponding to said wordlines, each drive means for driving a corresponding word line,activation means responsive to an externally applied row address signalfor selectively activating one of said drive means in said normal mode,and means for providing a plurality of multi-selection signals in a testmode, each of the plurality of multi-selection signals being provided toa corresponding word line group, said activation means being response tothe plurality of multi-selection signals in said test mode foractivating all the drive means corresponding to one of said word linegroups while maintaining inactive all the drive means corresponding tothe other of the word line groups.
 18. A semiconductor memory deviceincluding a normal mode and a test mode, said semiconductor memorydevice comprising:a semiconductor substrate, a plurality of word linesformed on said semiconductor substrate, a plurality of bit linescrossing said word lines, formed on said semiconductor substrate, aplurality of memory cells provided corresponding to respective crossingsof said word lines and said bit lines, each memory cell comprising acell capacitor including a cell plate and a storage node formed on saidsemiconductor substrate for storing data, and an access transistorincluding a gate electrode formed on said semiconductor substrate andconnected to a corresponding word line, one source/drain region formedin said semiconductor substrate and connected to a corresponding bitline, and another source/drain region formed in said semiconductorsubstrate and connected to the storage node of said cell capacitor, aplurality of drive means provided corresponding to said word lines, eachdrive means for driving a corresponding word line, activation meansresponsive to an externally applied row address signal in said normalmode for selectively activating one of said drive means, and responsiveto a predetermined multi-selection signal in said test mode foractivating at least two of said drive means independent of said rowaddress signal, substrate potential supply means responsive to saidmulti-selection signal for selectively supplying a predeterminedsubstrate potential and a predetermined first test potential to saidsemiconductor substrate, cell place potential generation means forgenerating a cell plate potential for said cell plate, and cell platepotential supply means responsive to said multi-selection signal forselectively supplying said cell plate potential from said cell platepotential generation means and a predetermined second test potential tosaid cell plate.